Water Rocket Forum

Welcome to the Water Rocket Forum, sponsored by The Water Rocket Achievement World Record Association.

The largest, most sophisticated and ground breaking group supporting you, the serious water rocket flyer! Whether you are a beginner or an expert, the WRA2 has something for everyone.

A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

It’s just an idea at the moment, but how about establishing a new class(s) with a limited air pressure and mass. In my opinion it’ll pave the ground for a very interesting competition. The main pros are safety and affordability. Competing in the open A class is out of the question for both reasons stated above for teams like ours where young people are actively involved.

I propose the following:

1) Rocket cannot exceed 1000 grams empty (no reaction mass).
2) Pressure is limited to 300psi. This is a kind of figure that can be easily achieved with domestic air pumps, but will be still safe for PVC, PP etc pipes. As well creating a vessel to hold this pressure will not require any exotic technology.
3) All other rules as in the A class (or B for this matter)

Sincerely I agree with the idea because there is a difficulty to work above 300 psi.
To work above 300psi you would need:
- carbon
- strong compressor
- money
- a big compsumtion of time around the rocket and the launcher

The difference between the rockets would be the nozzle, weight and drag. The best one on those settings with 300 psi would win.

There is a lot of stopped people because no one can pass easly the 300psi barrier.

I'm all for a new class too. I'm working on a class C entry right now, but honestly, flight duration is kind of lame. I'm not saying it isn't a real feat to keep a rocket in the air for 1:47, but altitude is what everyone really cares about.

I wouldn't say 300 psi is safe for PVC, though. I had one threaded fitting rupture at only 140 psi one time. Nor is it really that easy to produce 300 psi. If you are talking about the small compressors meant for car tires, they simply lie about what they will put out. Personally, I think 150 psi would be better. Any decent bike pump will do that, it's safer, and prevents "exotic technology" from having the advantage. I think you could make a lighter pressure vessel to hold even just 300 psi out of carbon fiber than you could out of PET.

I'd also throw out the suggestion of not requiring onboard video and a logging altimeter. People say you can find small video cameras real cheap, but I looked and found nothing. A flycamone2 cost me $100, and logging altimeters cost around $200. That's pretty expensive considering there are a lot of teenagers on here. If you could use peak altitude altimeters, you'd only have to spend $40 on a How High altimeter. I know you can get false peaks, and without the onboard video there is no way to verify the flight, but this would be more of a fun class. I think we can rely on the honour system here. You could also increase it to four flights instead of two, and if they aren't within a certain range, say 5%, then it doesn't count.

I just think that if you are going to make a class that's easier for the average Joe to enter, might as well make it real easy (and safe). Even if the less experienced members don't have much of a chance of winning, it would still be satisfying to build a rocket within a set of guidelines and see where you stand.

Well, parachute/streamer duration classes S3 and S6 exist in the FAI classification for space modelling. Personally I’m not interested in these classes for a very simple reason. Having a parachute in the air for a long period of time means a need for a large launch ground in most cases. It’s a bit difficult to find where we are based and around. In any case I think the C-class does have reasons for its existence.

Yes, indeed, some reasonable precautions have to be maintained when we are dealing with such pressure, but I still think that 300 psi are much much safer than figures required for competing in the A-class. It’s the same principle as in the propellant based rocketry: even a smallest rocket motor is dangerous if handled inappropriately.
In fact I can see a danger in lowering the pressure level to around 150psi. It is indeed easier to achieve, but it is right the upper border of what a water bottle is able to sustain. I think it may be tempting to push a little bit more and keep using bottles instead of employing safer technology. However, it might be a subject for this forum to discuss whether the limit can be set on 300psi or on a lower, for example 250psi, mark.
As for inaccuracy of air pumps, it is not a problem at all. Even if they lie, the real pressure will still be lower than the indicated level.

Another reason to set the limit on 300psi mark is that in fact it may not be a such advantage to pump in a higher pressure into a stronger pressure vessel. With a right design one might be able to build a rocket for a lover pressure trading it off for the rocket mass. This may lead to a very interesting technology development and thus to healthy competition.

I agree with you about onboard video . The video recording requirement constrains competition very much. Though, I’m not sure about a logging altimeter. I don’t have any experience with peak altimeters yet, and I don’t know their accuracy margin. However, out of my experience in other measurement systems I would think that more investigation is needed to establish a required number of attempts and accuracy range. In any case full details of any recording equipment and corresponding calibration data must be provided.

Personally I don’t want to simplify this class too much. I’d rather suggest setting-up another class or sub-class with a lover pressure margin.

The Sky Dart wrote:Well, parachute/streamer duration classes S3 and S6 exist in the FAI classification for space modelling. Personally I’m not interested in these classes for a very simple reason. Having a parachute in the air for a long period of time means a need for a large launch ground in most cases. It’s a bit difficult to find where we are based and around. In any case I think the C-class does have reasons for its existence.

Yes, indeed, some reasonable precautions have to be maintained when we are dealing with such pressure, but I still think that 300 psi are much much safer than figures required for competing in the A-class. It’s the same principle as in the propellant based rocketry: even a smallest rocket motor is dangerous if handled inappropriately.
In fact I can see a danger in lowering the pressure level to around 150psi. It is indeed easier to achieve, but it is right the upper border of what a water bottle is able to sustain. I think it may be tempting to push a little bit more and keep using bottles instead of employing safer technology. However, it might be a subject for this forum to discuss whether the limit can be set on 300psi or on a lower, for example 250psi, mark.
As for inaccuracy of air pumps, it is not a problem at all. Even if they lie, the real pressure will still be lower than the indicated level.

Another reason to set the limit on 300psi mark is that in fact it may not be a such advantage to pump in a higher pressure into a stronger pressure vessel. With a right design one might be able to build a rocket for a lover pressure trading it off for the rocket mass. This may lead to a very interesting technology development and thus to healthy competition.

I agree with you about onboard video . The video recording requirement constrains competition very much. Though, I’m not sure about a logging altimeter. I don’t have any experience with peak altimeters yet, and I don’t know their accuracy margin. However, out of my experience in other measurement systems I would think that more investigation is needed to establish a required number of attempts and accuracy range. In any case full details of any recording equipment and corresponding calibration data must be provided.

Personally I don’t want to simplify this class too much. I’d rather suggest setting-up another class or sub-class with a lover pressure margin.

Just to let everyone know, we are listening to this discussion.

A couple of recommendations on what has been discussed so far.

1. 250PSI might be a good limit for this class (a larger number of store bought compressors can reach 250 if used with care)

2. The onboard camera should stay (especially if it is decided that peak altimeters can be used) There are many low cost cameras out there. One does not need to use the flycam or the new HD cameras that some teams are beginning to fly. Most of the lower cost ones take lower resolution video (320x240) but that is sufficient for the competitions. Also the videos from the flights attract new people into the sport

3. With the pressure limited at 250 reinforcements can be accomplished using ordinary materials such as fishing line or tape keeping the cost down and construction time shorter.

Two more things to consider.

1. What do we call the competition. It needs to have a name that people would be proud to announce. "I am the WRA2 ____________ champion"

2. Will this new class draw class C competing teams and effectively "orphan" the class (lets hear from D & P and some of the other class C teams on this one).

Lisa Walker,Forum Administrator. The Water Rocket Achievement World Record Association

2. Attractiveness of the sport is definitely something we should consider when we discuss on-board video. With all contras another pro is that it'll make a result claim much easier.

With regard to other point:

1. How about a simple D-class? Or 250-class? I don't really think it's so important. That'll be a record any way.
2. I don't think so. It's really a question of how many members are able to launch without a risk of getting their rockets lost to trees etc.

The Sky Dart wrote:Well, parachute/streamer duration classes S3 and S6 exist in the FAI classification for space modelling. Personally I’m not interested in these classes for a very simple reason. Having a parachute in the air for a long period of time means a need for a large launch ground in most cases. It’s a bit difficult to find where we are based and around. In any case I think the C-class does have reasons for its existence.

Yes, indeed, some reasonable precautions have to be maintained when we are dealing with such pressure, but I still think that 300 psi are much much safer than figures required for competing in the A-class. It’s the same principle as in the propellant based rocketry: even a smallest rocket motor is dangerous if handled inappropriately.
In fact I can see a danger in lowering the pressure level to around 150psi. It is indeed easier to achieve, but it is right the upper border of what a water bottle is able to sustain. I think it may be tempting to push a little bit more and keep using bottles instead of employing safer technology. However, it might be a subject for this forum to discuss whether the limit can be set on 300psi or on a lower, for example 250psi, mark.
As for inaccuracy of air pumps, it is not a problem at all. Even if they lie, the real pressure will still be lower than the indicated level.

Another reason to set the limit on 300psi mark is that in fact it may not be a such advantage to pump in a higher pressure into a stronger pressure vessel. With a right design one might be able to build a rocket for a lover pressure trading it off for the rocket mass. This may lead to a very interesting technology development and thus to healthy competition.

I agree with you about onboard video . The video recording requirement constrains competition very much. Though, I’m not sure about a logging altimeter. I don’t have any experience with peak altimeters yet, and I don’t know their accuracy margin. However, out of my experience in other measurement systems I would think that more investigation is needed to establish a required number of attempts and accuracy range. In any case full details of any recording equipment and corresponding calibration data must be provided.

Personally I don’t want to simplify this class too much. I’d rather suggest setting-up another class or sub-class with a lover pressure margin.

Just to let everyone know, we are listening to this discussion.

A couple of recommendations on what has been discussed so far.

1. 250PSI might be a good limit for this class (a larger number of store bought compressors can reach 250 if used with care)

2. The onboard camera should stay (especially if it is decided that peak altimeters can be used) There are many low cost cameras out there. One does not need to use the flycam or the new HD cameras that some teams are beginning to fly. Most of the lower cost ones take lower resolution video (320x240) but that is sufficient for the competitions. Also the videos from the flights attract new people into the sport

3. With the pressure limited at 250 reinforcements can be accomplished using ordinary materials such as fishing line or tape keeping the cost down and construction time shorter.

Two more things to consider.

1. What do we call the competition. It needs to have a name that people would be proud to announce. "I am the WRA2 ____________ champion"

2. Will this new class draw class C competing teams and effectively "orphan" the class (lets hear from D & P and some of the other class C teams on this one).

Well, as for cheaper cameras being available, I couldn't find much else. You probably have a much greater selection in the US than other places. I've heard of people getting micro video cameras there in Walmart for under $30. There is nothing like that in a Canadian Walmart. Also, are these cheaper cameras generally heavier and larger? If so, the advantage still goes to the competitor with more money to spend. Perhaps you should try and find a cheap and easily available camera, and recommend it's use. People could use other cameras if they want, but they would have to carry extra dead weight if their camera was lighter. Just a thought.

250 psi seems reasonable to me.

As for the name, I also think class D is the obvious choice.

As for taking away from class C competitors, it might. I'm working on class C right now, but I might give up on it if this class started up. Probably not if logging altimeters were required, just because I don't have one. I just think altitiude competitions are more fun. And like Skydart said, you need a huge launch area for class C. I'm launching in giant farmers' fields right now, and I can still only go out when it's dead calm. Also, if you steal competitors from class c, it doesn't mean there are fewer people competing over all. The big question is, how many people who aren't competing at all now would compete in this class?

Alright, I take it back about the camera. I forgot about that "micro spy camera" on ebay. I can't remember why I decided not to go with that one. Maybe I was just willing to spend the extra money for what is probably a higher quality product. But anyone should be able to afford that, and it's even lighter than the FCO2.

So that leaves the altimeter. What if you accepted peak altitude altimeter readings, but made the rules tougher for them. For example, you could use a logging altimeter and the requirements would be the same as they are for Class A or Class B. However, if you used a peak altitude altimeter, you needed to do four consecutive flights, all within 10% of each other. I can't see false peaks from deployment or other causes being that consistent. You could also require the altimeter reading be shown on the ground based or on-board video.

I guess I keep thinking of younger competitors. I think they are far more likely to compete if it's cheap. I'm 18, and I know I am. But maybe there aren't enough young builders on here to justify it.

Why not just enter the 1000 foot competition? At those pressures you should be able to build a rocket to reach this heights. Is any body working on a 1000 foot rocket? Rocket session for me and I'm looking some friendly competition. Let me know if you are... so I can get pumped up again!!!

The Sky Dart wrote:OK. Are we moving anywhere, or the idea of a new class is officially dead? To be honest, I expected more interest from about 200 member teams.

Things are moving.

Typically when we make rules amendments they go in effect on the 1st of January so there is still time to discuss this preliminary new class. The timeline for this will be:

1. Allow more discussion in this thread for approximately 10 more days.

2. Post a "rough draft" of the rule set and allow a period of discussion.

3. Approve the new rules and post a final copy (this will most likely happen in November)

4. Officially start the competition on the 1st of January 2010. (teams CAN start constructing rockets prior to that once the approved rules are published but submissions will be accepted after January 1st.

I left this thread in the public area of the forum to encourage everyone to make suggestions (even non-members) so that a competition could be created that would attract even more people to join the WRA2 . The WRA2 is for everyone interested in water rocketry and not just die hard competitors

Lisa Walker,Forum Administrator. The Water Rocket Achievement World Record Association

The Sky Dart wrote:OK. Are we moving anywhere, or the idea of a new class is officially dead? To be honest, I expected more interest from about 200 member teams.

Things are moving.

Typically when we make rules amendments they go in effect on the 1st of January so there is still time to discuss this preliminary new class. The timeline for this will be:

1. Allow more discussion in this thread for approximately 10 more days.

2. Post a "rough draft" of the rule set and allow a period of discussion.

3. Approve the new rules and post a final copy (this will most likely happen in November)

4. Officially start the competition on the 1st of January 2010. (teams CAN start constructing rockets prior to that once the approved rules are published but submissions will be accepted after January 1st.

I left this thread in the public area of the forum to encourage everyone to make suggestions (even non-members) so that a competition could be created that would attract even more people to join the WRA2 . The WRA2 is for everyone interested in water rocketry and not just die hard competitors

reading this with interest although im a little confused about the cheap 250 psi compressors ( they dont exist where i live , cheap compressors are still $100 and are maximum 8 bar which is a long way shorrt of the 250 psi mark)